Obesity is a major health problem in the United States. It affects more than 30 million Americans, causes significant morbidity (e.g. diabetes and hypertension) and contributes to increased cardiovascular mortality. Unfortunately, however, current treatment approaches for obesity are not successful in producing long-term maintenance of weight loss. In this ongoing research, we have been developing and testing the effectiveness of innovative approaches to obesity treatment that depart significantly from traditional educational methods. These new approaches involve treatment strategies that directly modify the environmental cues and reinforcers that influence eating and exercise behaviors. Studies already completed have shown that directly modifying cues for eating by providing food and/or highly structured meal plans, markedly improves weight loss. The purpose of the present proposal is to extend this approach to two variables that are strongly related to weight loss maintenance, namely exercise and social support. Study one will evaluate whether weight loss and maintenance can be improved by 1) directly modifying cues for exercise, by using a "personal trainer" and/or 2) directly modifying reinforcement for exercise, by using a lottery system. Study two will investigate two new approaches to social support. One approach will modify social cues for eating and exercise by involving the entire family in a highly structured eating and exercise program. The second approach will modify social reinforcers by having participants work together to raise money for charity based on group attendance and treatment adherence. The proposed studies are unique in their emphasis on direct environmental intervention. They also are the first to evaluate comparative strategies for increasing exercise adherence and social support in obese patients, both of which are areas of great relevance to the maintenance of weight loss. It is believed that these studies will provide important data on procedures and processes that affect long-term change in diet, exercise and body weight. If successful, they may lead to improved treatments for obesity.